1. Field of the Invention
This invention relates generally to insulating devices and more particularly to shutter assemblies for windows, doors, and the like. Specifically, the subject invention relates to an improved interior shutter construction and assembly which provides exceptional and unexpected thermal insulation properties.
2. Description of the Prior Art
Energy conservation efforts have been increasing dramatically for a number of years. Such efforts are on a national scale and are attributable to several factors. One such factor is the increasing cost of oil. Another factor is the rapid depletion of many of our non-renewable energy resources, such as oil, gas and coal. Thus, for both conservation reasons as well as economic reasons, a great deal of effort is being expended in finding means for increasing the efficiency of heating and cooling plants as well as for reducing energy consumption.
One significant area of energy consumption involves the heating and cooling of building structures, such as homes, offices, industrial plants and the like. A major source of thermal energy loss in virtually all such existing buildings are the wall openings therein such as windows, doors and patio doors. While a great deal of effort has been directed to providing more efficient wall construction and insulation for such structures, such as illustrated in U.S. Pat. Nos. 2,172,048 and 4,160,349, it is only recently that serious efforts have been made to devise more efficient insulation mechanisms for wall openings. Prior to such recent efforts, the means utilized for insulating wall openings such as windows typically consisted of interior drapes and blinds or exterior window shutters, which also doubled as fireproof doors and burglar defeating devices. Examples of such devices are illustrated in U.S. Pat. Nos. 19,348, 858,287 and 996,781. However, such structures, usually metallic, provided very little thermal insulation or energy savings.
Wall openings such as patio doors, door windows and wall windows commonly include a single pane of glass. To determine the energy efficiency of such structures, a thermal resistance value (R-value) is measured, wherein the R-value is equal to the resistance to heat flow therethrough as defined by the following equation: ##EQU1## To illustrate the exceptionally large inefficiency of such glass window openings, the thermal resistance (R-value) of a normal insulated studded wall is about 11. The same R-value measurement for a double-paned glass window, as illustrated in U.S. Pat. No. 4,160,348, is only 1.8. Thus, even with a double-pane glass wall opening, the thermal energy (heat or air conditioning) losses are six times greater than the wall structure surrounding the opening. As another example, such a thermal loss is even twice as great as the loss through an uninsulated concrete floor. Adding a third pane to such a window structure would normally increase the R-value to approximately 2.4. However, such a structure is still much less energy efficient than the insulated wall structure surrounding the opening. Moreover, double and triple glazed windows reduce solar transmission significantly, with 10-15% of the incident radiation being filtered by each pane. Thus, multiple glazing may increase the R-value somewhat for insulation purposes, but it also reduces day-time capability of solar heating through solar transmission.
The more recent efforts to provide effective insulation for wall openings have generally been directed to adding a thermal cover to such a wall opening, for use particularly during night-time hours. One such thermal cover is marketed under the trademark "Window Quilt", by Appropriate Technology, Brattleboro, Vt. This device is a foil lined quilt that rolls down over the wall opening and is air sealed on all four sides. Apparently, the foil of this quilt reflects heat, and the seals create a large airspace for insulation between the quilt and the window. Such a quilt has an R-value of approximately 5.2, and this value is a significant increase in the thermal resistance factor as compared to a double or triple pane glass window. However, this is still substantially lower than the thermal resistance of an insulated wall structure itself. Thus, even when equipped with such a quilt, a wall opening will still be a source of significant thermal energy loss.
Moreover, such fabric or curtain approaches to movable window insulation in general have been severely limited in longevity by rapid deterioration due to alternate exposure to heat and cold (direct sunlight/below zero evening temperatures) and to dryness and moisture (direct sunlight/night condensation resulting from limited sealing capability). Such factors tend to crack and shrink the fabric and therefore destroy its sealing capability as well as deteriorate the product. Finally, cleaning of such fabric coverings is awkward and costly and tends to further accelerate product deterioration.
The present invention overcomes the aforementioned problems and insufficiencies and provides an energy efficient interior shutter assembly for covering a wall opening. The assembly of the present invention is constructed so as to provide an R-value of approximately 9.1-9.5. Thus, the thermal energy efficiency and conservation provided by the present invention is significantly better than any device heretofore known.